The present invention relates to a method of patterning, by using a mask, an object layer or object layers in a thin film element made of semiconductor material, conductive material, dielectric material or magnetic material. Particularly, the present invention relates to a patterning method for an object layer or layers in a thin film magnetic head and to a manufacturing method for a composite thin film magnetic head using the patterning method.
In dry etching or milling process, an object layer or object layers to be etched is partially coated by a patterned mask made of a resist such as photo-curing resin, and exposed parts of the layer or layers are chemically and/or physically eroded and removed by plasma beam or ion beam.
In the field of such dry etching, in general, an extremely directional etching process whereby side edges of the etched pattern become perpendicular to the surface of its under layer is called as an anisotropic etching (also called as a directional etching or a vertical etching).
For example, when recording magnetic pole layers of a composite thin film magnetic head with both an inductive recording head part and a magnetoresistive (MR) reproducing head part are patterned by such dry etching, a fine working for forming side edges precisely perpendicular to the substrate surface is required. Thus, in this process, it is necessary to use the anisotropic etching.
In the dry etching or milling process, since the mask layer itself is also etched as well as the object layer or layers, the mask layer has to be sufficiently thick. However, if the thickness of the mask layer increases, it is difficult to execute the anisotropic etching.
During etching process, etched materials from not only the object layer or layers but also the mask layer may be scattered and thus a part of the scattered materials may be redeposited on side edges of the mask layer causing the width of the mask layer to gradually increase. As a result, the anisotropy of the etching, which is necessary for patterning the object layer or layers, will be almost lost causing the side edges of the etched object layer or layers to become nonperpendicular to the surface of its under layer. In other words, the section of the etched object layer or layers will become a trapezoid shape in which its lower part width is longer than its upper part width.
In order to decrease the thickness of the mask layer, U.S. Pat. No. 5,141,623 proposes the use of a mask layer made of nickel-iron alloy which has a milling rate equal to the milling rate of the object layer to be etched. However, the nickel-iron mask layer itself will be also etched and the etched component will be redeposited on the side edges of the mask layer. Furthermore the nickel-iron mask layer cannot be made sufficiently thin but will have a thickness of 2-2.5 xcexcm. Thus, even if the nickel-iron mask layer is used, optimum anisotropy of the etching cannot be expected.
It is therefore an object of the present invention to provide a patterning method for at least one object layer and a manufacturing method for a composite thin film magnetic head using the patterning method, whereby side edges of the patterned layer becomes perpendicular to the surface of its under layer.
According to the present invention, a method of patterning at least one object layer, includes a step of forming a mask on the object layer, and a step of selectively etching the object layer using the mask. The mask is made of a magnetic metallic compound with a basic metal of nickel or cobalt containing at least group 3B element and/or group 5B element.
The magnetic metallic compound with a basic material of nickel metal or cobalt metal containing at least group 3B element and/or group 5B element has a milling rate extremely lower than that of the object layer or layers to milled. Thus, if such metallic compound is used for the material of the mask, the mask can be formed with very thin thickness. As a result, an excellent anisotropy can be surely expected.
Also, according to the present invention, a method of manufacturing a composite thin film magnetic head with an inductive recording head part and a magnetoresistive reproducing head part is provided. The method includes a step of forming recording magnetic pole layers of the thin film magnetic head, a step of forming a mask on the recording magnetic pole layers, and a step of selectively etching the recording magnetic pole layers using the mask. The mask is made of a magnetic metallic compound with a basic metal of nickel or cobalt containing at least group 3B element and/or group 5B element.
It is preferred that the group 3B element is boron, and/or that the group 5B element is phosphorus.
In this case, preferably, the mask has a composition containing 0.2 to 4.0 wt % of boron. Also, preferably, the mask has a composition containing 0.2 to 8.0 wt % of phosphorus.
If the weight composition of B contained in the NiB mask is 4.0 wt % or less, this NiB mask has magnetism. Also, if the weight composition of P contained in the NiP mask is 8.0 wt % or less, this NiP mask has magnetism. If the mask is made of such magnetic metallic compound, a very low milling rate that is extremely effective for the mask can be attained.
It is preferred that the object layer (or recording pole layers) includes an under layer for the mask, and that the under layer is made of an iron containing material such as nickel-iron, iron-nitrogen or iron-zirconium-nitrogen.
It is also preferred that the method further includes the steps of forming a resist frame with an opening portion in which the mask is to be formed on the object layer (or recording pole layers), forming the mask on the object layer (or recording pole layers) by an electroless plating process, and removing after the electroless plating process the resist frame.
It is also preferred that the method further includes the step of cleaning a surface to be plated by an acidic aqueous solution before the electroless plating process, and/or that a layer growing rate in the electroless plating process is kept at 100 nm/min or less.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.